Articoli di riviste: "Silicates"

1

Wooden, Diane H. "Cometary Silicates: Interstellar and Nebular Materials". Highlights of Astronomy 13 (2005): 495–97. http://dx.doi.org/10.1017/s1539299600016403.

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AbstractEvidence for interstellar material in comets is deduced from IR spectra, in situ measurements of Comet Halley, and chondritic porous interplanetary dust particles (CP IDPs). IR spectra of comets reveal the spectrally active minerals: amorphous carbon, amorphous silicates, and (in some comets) crystalline silicates. Evidence suggests amorphous silicates are of interstellar origin while crystalline silicates are of nebular origin.10 μm spectra of comets and sub-micron amorphous silicate spherules in CP IDPs have shapes similar to absorption spectra through lines-of-sight in the ISM. Thermal emission models of cometary IR spectra require Fe-bearing amorphous silicates. Fe-bearing amorphous silicates may be Fe-bearing crystalline silicates formed in AGB outflows that are amorphized through He+ ion bombardment in supernova shocks in the ISM.Crystalline silicates in comets, as revealed by IR spectra, and their apparent absence in the ISM, argues for their nebular origin. The high temperatures (>1000 K) at which crystals form or are annealed occur in the inner nebula or in nebular shocks in the 5 – 10 AU region. Oxygen isotope studies of CP IDPs show only 1% by mass of the silicate crystals are of AGB origin. Together this suggests crystalline silicates in comets are probably primitive grains from the early solar nebula.

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Niciu, H., Dorel Radu, C. Onose, A. Ioncea, Daniela Niciu, H. Stroescu e C. S. Onose. "The Permanently Bonded Glass Decor from Chemical Precursors". Advanced Materials Research 39-40 (aprile 2008): 579–82. http://dx.doi.org/10.4028/www.scientific.net/amr.39-40.579.

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Alkaline earth metal silicates as well as many polyvalent metals silicates can be obtained through aqueous solutions reactions between an alkaline silicate solution and the solutions of metal salts. The vitrifiation of the oxide compositions, established by the necessary molar ratios for the projected glass, is realised by calculating the concentration of chemical precursors, through their reaction directly on the substrate. The sodium silicate viscosity in aqueous solution and the viscosity of nitrogenated compounds or oxalates necessary in the silicates synthesis is compatible with the necessary viscosity for ink-jet cartridges. The necessary silicates forming reactions were studied directly on the deposition support, so that the functional characteristics of the multicompartment ink-jet cartridges were used. Compositions were realised, in which the colouring effect was obtained with ionic colorants. The vitrifiation and the quality of the obtained thin films were studied through Optical Microscopy and Scanning Electron Microscopy.

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Heckmann, W., F. Ramsteiner e Ch Mehler. "Morphology of Poly Amide Nanocomposites Characterized by Transmission Electron Microscopy (TEM) and Electron Spectroscopic Imaging (ESI)." Microscopy and Microanalysis 7, S2 (agosto 2001): 502–3. http://dx.doi.org/10.1017/s1431927600028580.

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The introduction of organophilic layered silicates into a polyamide matrix significantly improves stiffness and strength [1,2]. Two methods are known to prepare such nanocomposites. For both methods cations such as sodium, potassium, magnesium or calcium, located in the interlayer galleries of the layered silicates must be exchanged by quaternary alkyl ammonium ions containing at least one alkyl chain and so rendering the originally hydrophilic into an organophilic silicate. in the insitu-method monomeric caprolactam is intercalated between the modified silicate interlayers and subsequently polycondensated to polyamide. By this method the silicates can be broken down into their nanoscale building blocks as can be shown by TEM and ESI (Fig. 1). Another more direct possibility to delaminate the silicates is melt mixing in an extruder. with both methods similar degrees of delamination can be achieved.This paper presents some of our morphological results on polyamide containing organically modified montmorillonite.

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Molster, F. J. "Astromineralogy: Crystalline silicates". Symposium - International Astronomical Union 209 (2003): 291–98. http://dx.doi.org/10.1017/s0074180900208796.

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Silicates are the most abundant dust component in our Universe. For a long time it was generally assumed that around evolved stars only amorphous silicates were present. The infrared space observatory (ISO; Kessler et al. 1996) discovered that the abundance of crystalline silicates can be quite significant. Thanks to ISO it is now for the first time possible to determine the exact chemical composition of the silicates, and in contrast to the amorphous silicates, the crystalline silicates turned out to be very Fe-poor (i.e. forsterite and enstatite). Careful investigations of the spectra of crystalline silicates in several conditions, both in laboratory and in space, have taken place. It was found that not only the abundance of the crystalline silicates is related to the spatial distribution of the circumstellar dust, but also the shape of the features differs between sources with and without a disk-like dust distribution. Because of the many spectral features of the crystalline silicates one can easily determine temperatures and mass ratios for enstatite and forsterite. But even single features contain interesting information. The position and FWHM of the 69.0 micron forsterite feature, might be used as a new diagnostic of characteristic temperatures of (crystalline) silicate dust, while the 33.6 micron forsterite feature bears evidence for its formation history.

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Kemmitt, T., e NB Milestone. "The Ring Size Influence on 29Si N.M.R. Chemical Shifts of Some Spirocyclic Tetra- and Penta-coordinate Diolato Silicates". Australian Journal of Chemistry 48, n. 1 (1995): 93. http://dx.doi.org/10.1071/ch9950093.

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A series of tetracoordinate spirocyclic silicates has been prepared from the reaction of a range of diols with tetraethoxysilane, Si ( OEt )4. The silicates can be converted into anionic pentacoordinate silicates by reaction with KOBut/18-crown-6 in toluene. Alternatively, the pentacoordinate spirocycles can be prepared directly without prior preparation of a tetracoordinate spiro silicate. 29Si n.m.r. studies have demonstrated that the chemical shifts are sensitive to both coordination number and ring size. Ring contributions to the 29Si chemical shifts are apparent for the five- membered ring spiro silicates, those for the pentcoordinate species being less than those for the tetracoordinate species. Acyclic and six- membered ring spiro silicates are virtually indistinguishable by 29Si n.m.r. spectroscopy, which demonstrates that no ring contribution to the chemical shift is apparent for this ring size.

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6

Lii, Kwang-Hwa. "High-T, High-P Hydrothermal Synthesis of Uranium Silicates and Germanates". Acta Crystallographica Section A Foundations and Advances 70, a1 (5 agosto 2014): C759. http://dx.doi.org/10.1107/s2053273314092407.

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Most uranium minerals can be classified as oxidized species in which U is fully oxidized to U(VI), and reduced species, in which U occurs primarily as U(IV). Uranyl silicates are an important group of uranium(VI) minerals in the altered zones of many uranium deposits [1]. Uranyl silicates have also received attention because they form when spent nuclear fuel interacts with water containing silicon under oxidizing conditions. One naturally occurring uranium(IV) silicate exists, namely coffinite (USiO4), which is the most important ore mineral for uranium after uraninite. Numerous synthetic uranium(VI) silicates and germanates containing organic amines or alkali metals as countercations have also been reported [2]. In contrast to the uranium(VI) compounds, the chemistry of materials containing uranium(V) is considerably less developed owing to the tendency of U(V) to either oxidize to U(VI) or disproportionate to U(IV) and U(VI). We have synthesized a pentavalent-uranium silicate and a germanate by a high-temperature, high-pressure hydrothermal method in gold ampoules contained in a high-pressure reaction vessel at ca. 600 °C and 170 MPa [3a,b]. Following the synthesis of the U(V) compounds, a number of mixed-valence uranium silicates and germanates have been synthesized, for example, a mixed-valence uranium(IV,V) silicate, Cs2K(UO)2Si4O12 [3c], a uranium(IV,VI) germanate, Cs8U(UO2)3(Ge3O9)3·3H2O [3d], uranium(V,VI) silicates and germanates, A3(U2O4)Ge2O7 (A = Rb, Cs) and [Na9F2][(UO2)3(Si2O7)2] [3e,f], and a uranium(IV,V,VI) silicate, Na7UO2(UO)2(UO2)2Si4O16 [3g] in which three oxidation states of uranium co-exist in one compound. In addition, tetravalent-uranium compounds, Cs2USi6O15 and Cs4UGe8O20 [3h,i], were also synthesized. All members in the family of uranium silicates and germanates with the oxidation states of uranium from +4 to +6 have been observed. In this presentation the high-temperature, high-pressure hydrothermal synthesis, crystal structures, and XPS spectroscopy of these interesting compounds will be reported.

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Liang, Jian-Jie, Alexandra Navrotsky, Thomas Ludwig, Hans J. Seifert e Fritz Aldinger. "Enthalpy of Formation of Rare-earth Silicates Y2SiO5 and Yb2SiO5 and N-containing Silicate Y10(SiO4)6N2". Journal of Materials Research 14, n. 4 (aprile 1999): 1181–85. http://dx.doi.org/10.1557/jmr.1999.0158.

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The enthalpies of formation of two rare-earth silicates (Y2SiO5 and Yb2SiO5) and a N-containing rare-earth silicate Y10(SiO4)6N2 have been determined using high-temperature drop solution calorimetry. Alkali borate (52 wt% LiBO2·48 wt% NaBO2) solvent was used at 800 °C, and oxygen gas was bubbled through the melt. The nitrogen-containing silicate was oxidized during dissolution. The standard enthalpies of formation are for Y2SiO5, Yb2SiO5, and Y10(SiO4)6N2, respectively, –22868.54 ± 5.34, –22774.75 ± 8.21, and –14145.20 ± 16.48 kJ/mol from elements, and –52.53 ± 4.83, –49.45 6 ± 8.35, and –94.53 ± 11.66 kJ/mol from oxides (Y2O3 or Yb2O3, SiO2) and nitride (Si3N4). The silicates and N-containing silicate are energetically stable with respect to binary oxides and Si3N4, but the N-containing silicate may be metastable with respect to assemblages containing Y2SiO5, Si3N4, and SiO2. A linear relationship was found between the enthalpy of formation of a series of M2SiO5 silicates from binary oxides and the ionic potential (z/r) of the metal cation.

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8

P. C. Bennett, J. R. Rogers, W. J. "Silicates, Silicate Weathering, and Microbial Ecology". Geomicrobiology Journal 18, n. 1 (gennaio 2001): 3–19. http://dx.doi.org/10.1080/01490450151079734.

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9

Iliushchenko, V., L. Kalina, P. Hruby, V. Bilek Jr, J. Fladr, P. Bily e J. Bojanovsky. "The treatment of cementitious surface by selected silicate sealers". Journal of Physics: Conference Series 2341, n. 1 (1 settembre 2022): 012003. http://dx.doi.org/10.1088/1742-6596/2341/1/012003.

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Over the past decades, the efficiency of the silicate-based surface treatment agents, in other words, sealers, in concrete systems has been widely investigated. The surface treatment technology protects the cementitious systems against the penetration of undesirable substances. Nevertheless, understanding of the several aspects concerning silicate-based sealers is not entirely clear. This paper studies the action mechanism of selected silicates such as potassium, sodium, lithium water glasses, and colloidal silica. The effectiveness of used sealers in terms of water absorption reduction, the ability of silicates to heal pores, and the influence on the microstructure of the cement substrate were studied. Instrumental methods such as rheology, mercury intrusion porosimetry, or scanning electron microscopy were used to achieve satisfactory results. Nuances between the unique film-forming sealers were found. Colloidal silica showed a low sealing effect compared to alkali silicates.

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10

Jakobsen, U. H. "A hydrated barium silicate in unmetamorphosed sedimentary rocks of central North Greenland". Mineralogical Magazine 54, n. 374 (marzo 1990): 81–89. http://dx.doi.org/10.1180/minmag.1990.054.374.08.

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AbstractA new occurrence of barium silicates has been found in unmetamorphosed sedimentary rocks of central North Greenland. Two different barium minerals have been identified, the Ba-feldspar hyalophane, and an unknown and hitherto undescribed hydrated Ba-silicate with an anhydrous chemical composition identical to cymrite but with about 4 moles of water in the mineral structure. Both silicates are found in a black organic-rich chert sequence in close association with baryte. No replacement textures are observed between the three Ba-minerals.The hydrated Ba-silicate in the unmetamorphosed rock sequence of the Navarana Fjord area is considered to represent a member in a sequence of Ba-silicates from the unknown Ba-silicate with four H2O in the structure (BaAl2Si2O8·4H2O), through cymrite with one H2O (BaAl2Si2O2O8·H2O) to celsian with none (BaAl2Si2O8). This sequence might reflect the continuous release of water during prograde diagenesis and metamorphism. The association between chert and Ba minerals in the sedimentary rocks of the Navarana Fjord area is believed to reflect an addition of silica and barium by hydrothermal solutions.

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Baraček, Jan, Martin Palou, Jiří Másilko, Jaromír Wasserbauer, František Šoukal, Tomáš Opravil e Martin Boháč. "Application of Sol-Gel Method to Investigate the Influence of P₂O₅ on the Course of Reactions in CaO-SiO₂ System". Materials Science Forum 851 (aprile 2016): 92–97. http://dx.doi.org/10.4028/www.scientific.net/msf.851.92.

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The effect of P2O5 addition on the calcium silicate phase equilibrium during the sol-gel synthesis of dicalcium silicate was investigated using Scanning electron microscope and X-ray diffraction. It is established that phosphorous oxide can form solid solution with dicalcium silicate, but its causes the formation of phosphatic calcium silicate phases such as Ca14.92 (PO4)2.35(SiO4)5.65 and 5CaO.SiO2.P2O5 also. Local analysis has demonstrated the presence of calcium phosphate epicenters containing silicon oxide and calcium silicate zones with minimum content of phosphorous oxide and intermediary areas of various phosphatic calcium silicates. The formation of two distinct islets of calcium silicate and calcium phosphate is due to the affinity between acid oxides (SiO2, P2O5) and basic one (CaO) during sol-gel process. Then, the formation of various phosphatic calcium silicates result from the diffusion of P2O5 towards calcium silicate and that of SiO2 towards calcium phosphate.

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Shoshin, Evgeniy, Valeria Strokova, Denis Timokhin e Alexandr Strakhov. "Effect of Calcium Synthetic Hydro Silicate Additives on the Cement Systems’ Technological Characteristics". Materials Science Forum 1011 (settembre 2020): 59–65. http://dx.doi.org/10.4028/www.scientific.net/msf.1011.59.

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The use of finely dispersed fillers for cement concrete is accompanied not only by the cement binder saving, but also by a change in the technological characteristics of the cement mixtures. Depending on the nature of the additive used, both a positive and a negative water-reducing effect can be observed. The nature of the synthetic calcium silicates additives’ effect obtained by the method of sucrose-modified calcium hydro silicates thermolysis on the technological properties of the cement systems is considered. The independent methods determined the polymodal nature of the calcium silicates dispersions. The effect of the various dimensional scales particles on the technological properties of the cement system is determined. Micron particles affect the powder mixture compaction, the optimal content of calcium silicate additives is 20–40%. Nanometric particles, as well as residual freely extractable sucrose, determine the plasticizing effect of the synthetic calcium silicates additives introduction, the maximum manifestation of which is observed when the additive content is 20%. The visco-plastic properties of the “cement - synthetic calcium silicates” system’s mixtures were evaluated at various additive contents.

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Kozasa, Takashi, e Hisato Sogawa. "Formation of crystalline silicate around oxygen–rich AGB stars". Symposium - International Astronomical Union 191 (1999): 239–44. http://dx.doi.org/10.1017/s0074180900203124.

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Crystallization of silicate has been investigated within the framework of dust formation in steady state gas outflows around oxygen–rich AGB stars, where silicates are locked not only into homogeneous silicate grains but also into the mantles of heterogeneous grains. Based on the thermal history of dust grains after their formation, the crystallization calculation results in no crystalline silicate for the mass loss rate Ṁ ≤ 2 × 10−5M⊙ yr−1. Only silicate in the mantles of heterogeneous grains can be crystallized for Ṁ ≥ 3 × 10−5M⊙ yr−1, while homogeneous silicate grains remain amorphous. The mass fraction of crystalline silicate increases with increasing Ṁ. The radiation transfer calculations confirm the appearance of an emission feature around 33.5 μm, taking olivine as a representative of crystalline silicates. On the other hand, the 10μm feature appears in absorption, being dominated by homogeneous silicate grains. These trends are consistent with the observations. Thus the crystalline silicate is a diagnostics of high mass loss rate at the late stage of AGB stellar evolution, reflecting the formation process of dust grains.

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Vedyakov, Ivan, Vladimir Vaskalov, Nikolai Maliavski e Mikhail Vedyakov. "Highly Efficient Glass Ceramic Thermal Insulation". E3S Web of Conferences 263 (2021): 01017. http://dx.doi.org/10.1051/e3sconf/202126301017.

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Alkali-silicate thermal insulation materials (foam silicates) belong to the group of mineral heat insulators. Their main disadvantage is insufficient water resistance, to increase which special water-strengthening additives are introduced into materials. The aim of this work was to obtain and study foam silicates in granular (FGCG) and slab (FGCS) forms using a new production technology characterized by a simple one-stage technological scheme. Natural or technogenic amorphous silica, glassy sodium silicate (with the addition of carbonate or hydroxide) and a carbon-containing foaming agent, were used as the raw materials. Some part of the silica component was included in the binder solution, which made it possible to increase the silicate modulus in the final product to 5-10. This factor together with rather high Al2O3 concentration in the silica raw, made it possible to obtain foamed materials of very high water resistance. Another feature of the applied technology was a high foaming temperature (750–900°C). This factor makes a significant contribution to improving the water resistance of foam silicates, and significantly reducing their thermal conductivity and water absorption. As a result, FGCG was obtained with a bulk density of 170-440 kg/m3 (for FGCS – 300-400 kg/m3), a compressive strength in a cylinder of 0.5-6.3 MPa, a thermal conductivity of 0.046-0.084 W/(m·K) and a water absorption of 7.8-13.5% by volume. Mass loss of the specimens in boiling water was 0.12-0.33%, which puts obtained foamed materials on a par with most waterproof foam silicates being produced today.

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Khachatryan, L. A. "Disperse Layered Silicates in Magnesium Silicate Rocks". Glass Physics and Chemistry 30, n. 1 (gennaio 2004): 67–72. http://dx.doi.org/10.1023/b:gpac.0000016400.42044.5b.

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Borrmann, Thomas, Anton Dominis, Andrew J. McFarlane, James H. Johnston, Michael J. Richardson, Leon A. P. Kane-Maguire e Gordon G. Wallace. "Immobilisation of Fully Sulfonated Polyaniline on Nanostructured Calcium Silicate". Journal of Nanoscience and Nanotechnology 7, n. 12 (1 dicembre 2007): 4303–10. http://dx.doi.org/10.1166/jnn.2007.879.

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Up to 7.4% (w/w) of the sulfonated polyaniline, poly(2-methoxyaniline-5-sulfonic acid) (PMAS) can be absorbed onto nanostructured calcium silicates. Spectroscopic and leaching studies on the novel PMAS-silicate nanocomposites obtained indicate that attachment of the PMAS occurs via electrostatic binding of PMAS sulfonate groups to Ca2+ sites on the silicates. The surface area and pore volume of the nanocomposites are comparable to those of pure silicate and increase the surface area of the PMAS polymer by several orders of magnitude. The PMAS emeraldine salt in the nanocomposites retains its chemical reactivity, being readily oxidised and reduced to its pernigraniline and leucoemeraldine forms, respectively. The conductivity of the composite is comparable to that of the pure PMAS, several orders of magnitude higher than that of dried nanostructured calcium silicate.

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Okamoto, Tamami, e Shigeru Ida. "Monte Carlo Simulation of Dust Particles in a Protoplanetary Disk: Crystalline to Amorphous Silicate Ratio in Comets". Astrophysical Journal 928, n. 2 (1 aprile 2022): 171. http://dx.doi.org/10.3847/1538-4357/ac4bc1.

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Abstract The observationally inferred crystalline abundance in silicates in comets, which should have been formed in the outer region of a protoplanetary disk, is relatively high (∼10%–60%), although crystalline silicates would be formed by the annealing of amorphous precursors in the inner disk region. In order to quantitatively address this puzzle, we performed a Monte Carlo simulation of the advection/diffusion of silicate particles in a turbulent disk in a setting based on the pebble accretion model: pebbles consisting of many small amorphous silicates embedded in an icy mantle are formed in the outer disk region, silicate particles are released at the snow line, crystalline silicate particles are produced at the annealing line, silicate particles diffuse beyond the snow line, and they eventually stick to drifting pebbles to return to the snow line. In the simple case without sticking and with steady pebble flux, we show through the simulations and analytical arguments that the crystalline components in silicate materials beyond the snow line are robustly and uniformly ≃5%. On the other hand, in a more realistic case with sticking and with a decaying pebble flux, the crystalline abundance increases to ∼20%–25%, depending on the ratio of the decay to diffusion timescales. This abundance is consistent with the observations. In this investigation, we assume a simple steady-accretion disk. The simulations coupled with the disk evolution are needed for a more detailed comparison with observed data.

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DERRIEN, RICHARD, ETHAN MICHAEL SULLIVAN, STEPHEN LIU, ELODIE MOINE e FRANCIS BRIAND. "Silicate Island Formation in Gas Metal Arc Welding". Welding Journal 100, n. 01 (1 gennaio 2021): 13–26. http://dx.doi.org/10.29391/2021.100.002.

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Because formation of silicate islands during gas metal arc welding is undesirable due to decreased productivity and decreased quality of welds, it is important to understand the mechanism of the formation of these silicate islands to mitigate their presence in the weld. The effects of welding parameters on the silicate formation rate were studied. Results showed that the applied voltage and oxidizing potential of the shielding gas were the parameters that most strongly influenced the amount of silicates formed on the surface of the weld bead. High-speed video was used to observe the formation of silicate islands during the welding process, which showed that the silicates were present at each stage of the welding process, including the initial melting of the wire electrode, and grew by coalescence. A flow pattern of the silicate islands was also proposed based on video analysis. An electromagnetic levitation system was used to study the growth kinetics of the silicate islands. Silicate coverage rate was found to increase with increasing oxidizing time, increasing oxidizing potential of the atmosphere, and increasing content of alloying elements except for Ti.

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Hawthorne, Frank C., Yulia A. Uvarova e Elena Sokolova. "A structure hierarchy for silicate minerals: sheet silicates". Mineralogical Magazine 83, n. 1 (9 novembre 2018): 3–55. http://dx.doi.org/10.1180/mgm.2018.152.

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AbstractThe structure hierarchy hypothesis states that structures may be ordered hierarchically according to the polymerisation of coordination polyhedra of higher bond-valence. A hierarchical structural classification is developed for sheet-silicate minerals based on the connectedness of the two-dimensional polymerisations of (TO4) tetrahedra, where T = Si4+ plus As5+, Al3+, Fe3+, B3+, Be2+, Zn2+ and Mg2+. Two-dimensional nets and oikodoméic operations are used to generate the silicate (sensu lato) structural units of single-layer, double-layer and higher-layer sheet-silicate minerals, and the interstitial complexes (cation identity, coordination number and ligancy, and the types and amounts of interstitial (H2O) groups) are recorded. Key aspects of the silicate structural unit include: (1) the type of plane net on which the sheet (or parent sheet) is based; (2) the u (up) and d (down) directions of the constituent tetrahedra relative to the plane of the sheet; (3) the planar or folded nature of the sheet; (4) the layer multiplicity of the sheet (single, double or higher); and (5) the details of the oikodoméic operations for multiple-layer sheets. Simple 3-connected plane nets (such as 63, 4.82 and 4.6.12) have the stoichiometry (T2O5)n (Si:O = 1:2.5) and are the basis of most of the common rock-forming sheet-silicate minerals as well as many less-common species. Oikodoméic operations, e.g. insertion of 2- or 4-connected vertices into 3-connected plane nets, formation of double-layer sheet-structures by (topological) reflection or rotation operations, affect the connectedness of the resulting sheets and lead to both positive and negative deviations from Si:O = 1:2.5 stoichiometry. Following description of the structural units in all sheet-silicate minerals, the minerals are arranged into decreasing Si:O ratio from 3.0 to 2.0, an arrangement that reflects their increasing structural connectivity. Considering the silicate component of minerals, the range of composition of the sheet silicates completely overlaps the compositional ranges of framework silicates and most of the chain-ribbon-tube silicates.

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Marler, Bernd, Melanie Müller e Hermann Gies. "Structure and properties of ITQ-8: a hydrous layer silicate with microporous silicate layers". Dalton Transactions 45, n. 25 (2016): 10155–64. http://dx.doi.org/10.1039/c6dt00713a.

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Dunn, Pete J. "The lead silicates from Franklin, New Jersey: occurrence and composition". Mineralogical Magazine 49, n. 354 (dicembre 1985): 721–27. http://dx.doi.org/10.1180/minmag.1985.049.354.12.

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AbstractThe lead silicate minerals from Franklin, New Jersey, occurred in two separate assemblages. One of these is characterized by esperite associated with hardystonite and occasional larsenite. The second assemblage can be considered as two parts: one consists of margarosanite, barysilite, nasonite, and ganomalite; the other contains roeblingite and hancockite, together with a number of highly hydrated phases. Chemical analyses indicate that these species conform to their theoretical compositions. There are no simple lead silicates at Franklin; all are compound silicates of Pb with Mn, Zn, and Ca.

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Payan, François, Albert Issa, Jean-Marc Krafft, Yannick Millot, Thomas Onfroy, Capucine Sassoye, Jean-François Hochepied, Guillaume Laugel e Hélène Lauron-Pernot. "Controlling Magnesium Silicates Coprecipitation Conditions: A Tool to Tune Their Surface Acid–Base Reactivity". Catalysts 13, n. 11 (25 ottobre 2023): 1393. http://dx.doi.org/10.3390/catal13111393.

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Magnesium silicates combining acidic and basic surface properties are known to be interesting as heterogeneous catalysts. Nevertheless, their catalytic performances are highly dependent on the synthesis method used. In this study, a series of magnesium silicates was synthesized for the first time using a coprecipitation method with a micromixer. It is first shown that changes in synthesis/precipitation pH led to magnesium silicates with different Mg/Si ratios: the higher the synthesis pH, the higher the Mg/Si ratio. Moreover, prepared silicates with a final Mg/Si ratio greater than 0.7, thus prepared at high pH, exhibit negligible specific surface area, whereas relatively high values (>180 m2/g) have been obtained for lower Mg/Si ratios. A set of experimental characterization data obtained by N2 physisorption, SEM, XRD, TGA-DTA as well as Raman and 29Si NMR spectroscopies are presented and discussed. They show the existence of two distinct families with a similar Magnesium Silicate Hydrate (MSH) phase, but they reveal different aggregation states and textural properties. Finally, the surface acid–base reactivity of the co-precipitated magnesium silicates was determined using the model reaction of 2-methylbut-3-yn-2-ol (MBOH) conversion. The results obtained suggest that it is possible to prepare silicates with a wide range of surface acid–base properties, from purely basic solids to those with both acidic and basic properties, by adjusting the final Mg/Si ratio via the control of the synthesis parameters.

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Gotlib, Elena, Dilyara Sadykova, Ekaterina Yamaleeva e Alla Sokolova. "Modification of polyvinylchloride by the silicates on the base of rice husk". E3S Web of Conferences 263 (2021): 01001. http://dx.doi.org/10.1051/e3sconf/202126301001.

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As a modifying additive in PVC-compositions, silicates produced by means of rice husk processing are of practical interest. Rice husk ash obtained by burning at 350°C, along with synthetic and naturally occurring wollastonite, significantly reduce plasticizer’s migration from the PVC-composition due to their porosity. This is due to the fact that the part of hydroxyl components of the plasticizer EDOS has adsorbed on the surface or retained by the silicates pores. Along with that, Miwoll 10-97 ensures a greater decrease in plasticizer’s migration than synthetic calcium silicate on the base of rice husk ash. When all the researched silicates are modified by the rice husk and naturally occurring wollastonite, heat stability of PVC-compositions grows. This is preconditioned by the alkaline origin of the surface of filling compounds that allows their possible reaction with chlorine hydride released from PVC during thermal decomposition. Synthetic and naturally occurring wollastonite enhance strain-strength properties of PVC-compositions whereas silicates on the case of rice husk reduce these parameters.

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Liu, Yongjun, Wenping Luo, Jiali Wu, Yewen Fang, Yan Li, Xiaoping Jin, Li Zhang, Zongyong Zhang, Fenfen Xu e Chan Du. "Radical addition-polar termination cascade: efficient strategy for photoredox-neutral-catalysed cyclopropanation and Giese-type reactions of alkenyl N-methyliminodiacetyl boronates". Organic Chemistry Frontiers 7, n. 13 (2020): 1588–92. http://dx.doi.org/10.1039/d0qo00349b.

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Abstract (sommario):

Silicate meets boronate: efficient cyclopropanation and Giese-type reactions of alkenyl N-methyliminodiacetyl boronates with alkyl silicates have been realized via a photoredox-neutral-catalysed radical-polar crossover process.

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25

Plášil, Jakub. "Mineralogy, Crystallography and Structural Complexity of Natural Uranyl Silicates". Minerals 8, n. 12 (27 novembre 2018): 551. http://dx.doi.org/10.3390/min8120551.

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Abstract (sommario):

Naturally occurring uranyl silicates are common constituents of the oxidized parts (i.e., supergene zone) of various types of uranium deposits. Their abundance reflects the widespread distribution of Si4+ in the Earth’s crust and, therefore, in groundwaters. Up to date, 16 uranyl silicate minerals are known. Noteworthy is that the natural uranyl silicates are not extremely diverse regarding their crystal structures; it is a result of possible concentrations (activity) of Si4+ in aqueous solutions derived from dissolution of primary Si minerals or the composition of late hydrothermal fluids. Therefore, in natural systems, we distinguish in fact among two groups of uranyl silicate minerals: uranophane and weeksite-group. They differ in U:Si ratio (uranophane, 1:1; weeksite, 2:5) and they form under different conditions, reflected in distinctive mineral associations. An overview of crystal-chemistry is provided in this paper, along with the new structure data for few members of the uranophane group. Calculations of the structural complexity parameters for natural uranyl silicates are commented about as well as other groups of uranyl minerals; these calculations are also presented from the point of view of the mineral paragenesis and associations.

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26

Garbalińska, Halina, Jarosław Strzałkowski e Agata Stolarska. "Moisture Influence on Compressive Strength of Calcium Silicate Masonry Units–Experimental Assessment and Normative Calculations". Materials 13, n. 17 (29 agosto 2020): 3817. http://dx.doi.org/10.3390/ma13173817.

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Abstract (sommario):

This paper primarily assesses the scale of adverse changes to the compressive strength of different types of silicates due to the influence of moisture. The study covers three groups of silicate units of different strength classes—15, 20 and 25—obtained from three different manufacturers. It was demonstrated that in all studied groups, moisture significantly decreased the compressive strength by about 30–40%. In addition, microstructural studies were conducted to analyze the relationship between the specific porosity structure of each group of silicate bricks and their compressive strength. On the basis of SEM (Scanning Electron Microscopy) and EDS (Electron Dispersive Spectroscopy) analysis, the elemental composition of individual silicates was determined and the contact zone between the aggregate and the binder was determined, which largely influenced the obtained compressive strength of each silicates. Next, the study referred to the utility of the normative procedure used to determine the strength class of samples with different geometries and at different moisture concentrations. The results of the calculations showed the high accuracy of the normative-based assessment of strength class, regardless of the manufacturer and the moisture values during examination.

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27

Li, Chao-Feng, Lian-Jun Feng, Xuan-Ce Wang, Simon-A. Wilde, Zhu-Yin Chu e Jing-Hui Guo. "A low-blank two-column chromatography separation strategy based on a KMnO4 oxidizing reagent for Cr isotope determination in micro-silicate samples by thermal ionization mass spectrometry". Journal of Analytical Atomic Spectrometry 32, n. 10 (2017): 1938–45. http://dx.doi.org/10.1039/c7ja00225d.

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28

Mor, Nitu, Prabhjot Kaur, Daljeet Kaur, Jitender Sharma e Sunita Dalal. "Isolation of silicate solubilising microbes (SSM) from soil and water samples as potential components of bio fertilizers". Research Journal of Chemistry and Environment 28, n. 7 (31 maggio 2024): 94–100. http://dx.doi.org/10.25303/287rjce0940100.

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Abstract (sommario):

Silicate solubilizing microbes (SSM) are crop beneficial microbes which facilitate silica uptake via plant roots by way of dissolving silicates and making it available in the form of monomeric silicic acid. Excessive use of synthetic fertilizers may negatively affect overall soil health and the environment. To ensure that crops provide competitive yields while preserving the ecological balance of the soil, it is necessary to develop and use bio-fertilizers. For this, a consortium is required which can solubilise complex form of phosphates, silicates etc. to provide important nutrients to crops while simultaneously maintaining the soil balance. In the present study, silicate producing microorganisms (Bacteria/Fungi) were isolated from different sites including water bodies and different soils. The samples were enriched with different agro-residues prior to isolation. Two different screening methods were used to select solubilising silicate bacteria (SSB) and solubilising silicate fungi (SSF). SSB producing the maximum zone of silicate dissolution were characterized and identified while SSF were selected on the basis of colour change in silica peptone broth. A total of four two bacteria (SSB) and two fungi (SSF) with potential of silicate solubilisation were isolated, screened, characterized and identified.

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29

E. Sangok, Faustina, Sabrina M. Yahaya, Izza Taib Nurul, Siti Zaleha Sa'ad e Nor Fazila Rasaruddin. "Comparison Study of Amino-Functionalized and Mercaptopropyl-Functionalized Mesoporous Silica MCM-41". Advanced Materials Research 550-553 (luglio 2012): 1603–6. http://dx.doi.org/10.4028/www.scientific.net/amr.550-553.1603.

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Abstract (sommario):

The ability to decorate silicate surface with different organoalkoxysilanes creates powerful new capabilities for catalyst, adsorbents and chemical separation. Mesopororus silica, MCM-41 was modified by grafting of amino and mercaptopropyl functional group. The structures of these materials were characterized by using Fourier Transform Infrared Spectroscopy (FT-IR), and X-Ray diffraction (XRD). The samples were found to exhibit structural properties similar to those reported earlier. Significant functional groups of the modified mesoporous silicates were found in the spectrum of FT-IR. Standard structure of mesoporous silicates were found to be preserved at planar [100] of XRD difractogram of mesoporous silicates. Adsorption of Cu (II) ions were done under different temperatures, initial concentrations and pH. Adsorption process also was determined from kinetic point of view and was found to be better fitted to pseudo second order of kinetic model.

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30

Malik, Priya, Supriya Sehrawat, Aryan Boora, Bhavna Anisha, Sushma Kumari, Yogesh Ahlawat e Surender Duhan. "Optical and structural properties of Nd2O3-SiO2 nanocomposite as synthesized from sol-gel technique". Zastita materijala 64, n. 4 (2023): 512–18. http://dx.doi.org/10.5937/zasmat2304512m.

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Abstract (sommario):

Nd2O3-SiO2 nanocomposite was prepared in the current work utilising the sol-gel technique. After being heated in air, the amorphous phase of silicates transformed to crystalline phase via intermediate phase as oxide. Due to its comparatively small operating temperature and ability to form nanostructures with precise size, sol-gel approach is a compelling alternative. X-ray powder diffraction (XRD), Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), which verified the structural characteristics of neodymium silicate (Nd2O3-SiO2) nanocomposites, were used to characterise the synthesised materials. The effect of duration and annealing temperature on the phase advancement of the silicates has been considered thoroughly. It was discovered that the sample was sintered for 3 hours at various temperatures, thus obtaining neodymium silicates. In addition, Optical characterization of Nd2O3 -SiO2 was performed using Photoluminescence Spectroscopy (PL).

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31

Wagh, Arun S., e Victor E. Douse. "Silicate bonded unsintered ceramics of Bayer process waste". Journal of Materials Research 6, n. 5 (maggio 1991): 1094–102. http://dx.doi.org/10.1557/jmr.1991.1094.

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Abstract (sommario):

Sodium silicates are investigated to enhance the strengths of Bayer process muds and develop structural ceramics without sintering. With an impregnation of sodium silicate from 2% to 10% concentration in red mud, the fracture toughness is enhanced from 0.2 to 0.9 MPa. Compression strengths of 25.1 MPa (3628 psi) have been attained with red mud at 10% silicate concentration. Similar enhancements by a factor of 4 to 5 have been obtained for modulus of rupture and Brinell hardness number. It is shown that these properties do not deteriorate in acidic and neutral environment in water, implying stability to weathering conditions. SEM investigations reveal elongated crystal formation, possibly of aluminum and iron silicates in the aggregate. These crystals act like whiskers enhancing the strength. The process is applicable for development of low-cost construction components.

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32

Ganter, Markus, Wolfram Gronski, Peter Reichert e Rolf Mülhaupt. "Rubber Nanocomposites: Morphology and Mechanical Properties of BR and SBR Vulcanizates Reinforced by Organophilic Layered Silicates". Rubber Chemistry and Technology 74, n. 2 (1 maggio 2001): 221–35. http://dx.doi.org/10.5254/1.3544946.

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Abstract (sommario):

Abstract Rubber compounds based on butadiene rubber (BR) or styrene—butadiene rubber (SBR) containing organophilic layered silicates were prepared. Organophilic silicates were swollen in a rubber/toluene solution. Matrix—filler reactive bonding was performed by adding bis(triethoxysilylpropyl)-tetrasulfan (TESPT) during swelling. Excellent dispersion of organoclay nanofillers in rubber matrices was demonstrated by transmission electron microscopy (TEM) and atomic force microscopy (AFM) exhibiting intercalated and partially exfoliated silicate layers. Matrix—filler interfacial coupling by TESPT led to reduced strain at break and reduced hysteresis for both organoclay and silica-based vulcanizates as expected for successful matrix filler coupling. Organoclay vulcanizates exhibited enhanced hysteresis when compared to silica compounds. This is related to orientation and sliding of anisotropic silicate layers, as determined by online wide-angle X-ray scattering (WAXS) measurements during cyclic tensile testing.

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33

Sanghani, Manish N., Luc Lajaunie, Kuljeet Kaur Marhas, William D. A. Rickard, Silver Sung-Yun Hsiao, Zan Peeters, Hsien Shang, Der-Chuen Lee, José J. Calvino e Martin Bizzarro. "Microstructural and Chemical Investigations of Presolar Silicates from Diverse Stellar Environments". Astrophysical Journal 925, n. 2 (31 gennaio 2022): 110. http://dx.doi.org/10.3847/1538-4357/ac3332.

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Abstract (sommario):

Abstract We report the structural and chemical investigation of nine presolar silicate grains from the CH3/CBb3 chondrite Isheyevo and CR2 chondrite Northwest Africa (NWA) 801. Five of these grains belong to group 1, likely condensed in low- to intermediate-mass asymptotic giant branch (AGB) stars, super-AGB stars, or core-collapse supernovae, while the remaining four grains belong to group 4 and have a supernova origin. The advanced transmission electron microscopy and associated electron spectroscopy analyses show a diverse range of chemical and structural compositions for presolar silicates. Two GEMS (glass with embedded metal and sulfide)-like silicates, each from different groups, condensed under nonequilibrium conditions in stellar outflows. Two nonstoichiometric silicates from group 1 have dissimilar formation and alteration histories. An amorphous silicate from group 1 with olivine-like [(Mg,Fe)2SiO4] composition likely formed as a crystalline olivine that subsequently amorphized in the interstellar medium. An oldhamite (CaS) grain within a stoichiometric enstatite (MgSiO3) from group 1 probably formed by heterogeneous condensation in circumstellar outflows. Of the two crystalline grains from group 4, one is an antigorite [(Mg,Fe)3Si2O5(OH)4], while the other is a nontronite [Na,Fe2(Si,Al)4O10(OH)2.nH2O], both formed as a crystalline forsterite and later altered to have hydrated silicate composition. A group-4 silicate has a chemical composition similar to a low Ca-pyroxene [(Ca,Mg)(Si,Al)2O6]. Our data imply that presolar grains from different groups can have a similar range of grain-formation conditions.

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Champness, P. E., e R. W. Devenish. "Elemental mass loss in silicate minerals during x-ray analysis". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 4 (agosto 1990): 804–5. http://dx.doi.org/10.1017/s0424820100177155.

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Abstract (sommario):

It has long been recognised that silicates can suffer extensive beam damage in electron-beam instruments. The predominant damage mechanism is radiolysis. For instance, damage in quartz, SiO2, results in loss of structural order without mass loss whereas feldspars (framework silicates containing Ca, Na, K) suffer loss of structural order with accompanying mass loss. In the latter case, the alkali ions, particularly Na, are found to migrate away from the area of the beam. The aim of the present study was to investigate the loss of various elements from the common silicate structures during electron irradiation at 100 kV over a range of current densities of 104 - 109 A m−2. (The current density is defined in terms of 50% of total current in the FWHM probe). The silicates so far ivestigated are:- olivine [(Mg, Fe)SiO4], a structure that has isolated Si-O tetrahedra, garnet [(Mg, Ca, Fe)3Al2Si3AO12 another silicate with isolated tetrahedra, pyroxene [-Ca(Mg, Fe)Si2O6 a single-chain silicate; mica [margarite, -Ca2Al4Si4Al4O2O(OH)4], a sheet silicate, and plagioclase feldspar [-NaCaAl3Si5O16]. Ion- thinned samples of each mineral were examined in a VG Microscopes UHV HB501 field- emission STEM. The beam current used was typically - 0.5 nA and the current density was varied by defocussing the electron probe. Energy-dispersive X-ray spectra were collected every 10 seconds for a total of 200 seconds using a Link Systems windowless detector. The thickness of the samples in the area of analysis was normally 50-150 nm.

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35

Mishagin, Kirill, Elena Gotlib, Ekaterina Yamaleeva, Alla Sokolova e Aleksey Khatsrinov. "Comparison of the Properties of Calcium Silicates Derived from Different Raw Materials". E3S Web of Conferences 410 (2023): 01001. http://dx.doi.org/10.1051/e3sconf/202341001001.

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Abstract (sommario):

The limited deposits of natural wollastonite in our country and the labor intensity of its extraction and processing, make promising the development of methods of its synthesis based on various types of domestic plant and fossil raw materials, especially industrial waste. The use of rice husk ash and calcium oxide in the solid-phase synthesis of calcium silicates ensures the content of β-wollastonite in their composition at the level of naturally-occurring Miwoll10-97. The obtained results indicate greater efficiency of amorphous silicon dioxide for the synthesis in the solid phase of calcium silicates. Synthetic calcium silicates, like naturally occurring wollastonite, have a pronounced alkaline surface nature, with the acid-base characteristics not influenced significantly by the sintering temperature, as well as the type and ratio of initial components. Calcium silicate produced from zeolite-siliceous rock has the smallest particle size and the narrowest particle size distribution, i.e. the most homogeneous structure. All investigated calcium silicates increase the wear resistance of epoxy materials, and low-porous silica sand-based fillers are more effective, providing high resistance of filled epoxy materials to climatic factors as well.

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36

Simachev, A. S., T. N. Oskolkova, A. A. Umanskii e A. V. Golovatenko. "Non-metallic inclusions in different zones of crystallization of E90KhAF rail steel". Izvestiya. Ferrous Metallurgy 64, n. 2 (2 aprile 2021): 135–42. http://dx.doi.org/10.17073/0368-0797-2021-2-135-142.

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Abstract (sommario):

Metallographic and X-ray studies of continuously cast billets of E90KhAF rail steel have been carried out. We have established the regularities of non-metallic inclusions distribution over the crystallization zones before and after billets deformation. It was revealed that in crustal zone the main non-metallic inclusions are point oxides, aluminum nitrides, iron silicates (FeO·SiO2) and alumosilicates (Al2O3·SiO2). They were identified in the zone of columnar crystals. In central zone of the billet, manganese sulfides (MnS), manganese silicates (MnO·SiO2), alumosilicates (Al2O3·SiO2), iron silicates (FeO·SiO2), and point oxides were found. It has been determined that concentration and size of nonmetallic inclusions tend to increase from the surface to central zone of continuously cast billets, which is consistent with generally accepted ideas about mechanisms of billet formation during crystallization. The mechanism of deformation of two-phase silicate non-metallic inclusions and their influence on quality of rail products was disclosed. It is shown that inhomogeneous deformability of complex silicate inclusions aggravates their harmful effect on rail products quality. In this case, additional stresses appear in addition to inclusion-matrix deformation and contact stresses existing at interphase boundaries. This pattern also holds for non-deformed silicate inclusions. Such a distribution of inclusions in the billets volume somewhat reduces their negative effect on rails quality, since near-contact layers of the billet undergo more intense deformation during rolling, and as the axial zone of a billet is approached, deformation rate decreases.

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Mihailova, Irena, e Dimitar Mehandjiev. "Catalytic activity of Co-åkermanite and Co-pyroxene in oxidation reactions". Canadian Journal of Chemistry 89, n. 8 (agosto 2011): 939–47. http://dx.doi.org/10.1139/v11-061.

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Abstract (sommario):

Two calcium–cobalt silicates were synthesized in which cobalt occupies different structural positions. The crystal phases belong to two main structural silicate types. In the Co-åkermanite structure (Ca2CoSi2O7), cobalt cations take tetrahedral coordination toward oxygen atoms. In the Co-pyroxene structure of CaCoSi2O6, cobalt displays octahedral coordination. Ca2CoSi2O7 was prepared by solid-phase synthesis and CaCoSi2O6 was prepared by sol–gel method. The synthesis of the phases was confirmed by XRD, FTIR, and EPR data. On the basis of the XPS analysis, it can be concluded that Co2+ cations exist in the studied silicates. Thus, it is possible to study the catalytic activity of two silicate phases containing Co2+ cations in different coordinations: tetrahedral and octahedral. It was found that cobalt silicates with crystal structures corresponding to pyroxene and åkermanite possess catalytic activity in the reactions of complete oxidation of CO and toluene. Co-pyroxene exhibits higher catalytic activity than Co-åkermanite, but the higher cobalt content on the surface of Co-pyroxene should also be taken into account. Then, it turns out that catalytically active complexes with Со2+ ions in tetrahedral coordination are more efficient than those with such ions in octahedral coordination when equal concentrations of cobalt were used on the surface of the catalysts.

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38

Almeida Streitwieser, Daniela, Arturo Arteaga, Alvaro Gallo-Cordova, Alexis Hidrobo e Sebastian Ponce. "Chemical Recycling of Used Motor Oil by Catalytic Cracking with Metal-Doped Aluminum Silicate Catalysts". Sustainability 15, n. 13 (4 luglio 2023): 10522. http://dx.doi.org/10.3390/su151310522.

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Abstract (sommario):

The chemical recycling of used motor oil via catalytic cracking to convert it into secondary diesel-like fuels is a sustainable and technically attractive solution for managing environmental concerns associated with traditional disposal. In this context, this study was conducted to screen basic and acidic-aluminum silicate catalysts doped with different metals, including Mg, Zn, Cu, and Ni. The catalysts were thoroughly characterized using various techniques such as N2 adsorption–desorption isotherms, FT-IR spectroscopy, and TG analysis. The liquid and gaseous products were identified using GC, and their characteristics were compared with acceptable ranges from ASTM characterization methods for diesel fuel. The results showed that metal doping improved the performance of the catalysts, resulting in higher conversion rates of up to 65%, compared to thermal (15%) and aluminum silicates (≈20%). Among all catalysts, basic aluminum silicates doped with Ni showed the best catalytic performance, with conversions and yields three times higher than aluminum silicate catalysts. These findings significantly contribute to developing efficient and eco-friendly processes for the chemical recycling of used motor oil. This study highlights the potential of basic aluminum silicates doped with Ni as a promising catalyst for catalytic cracking and encourages further research in this area.

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JIA, FEIFEI, e SHAOXIAN SONG. "EXFOLIATION AND CHARACTERIZATION OF LAYERED SILICATE MINERALS: A REVIEW". Surface Review and Letters 21, n. 02 (aprile 2014): 1430001. http://dx.doi.org/10.1142/s0218625x14300019.

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Abstract (sommario):

Exfoliated silicate minerals have attracted great attentions because of the dramatic improvement in properties. This paper highlights the preparation of exfoliated silicate minerals, including physical, chemical, mixed physical and chemical methods. The mechanisms by which silicates are exfoliated and the important influential factors are also summarized. Finally, the instrumental techniques to characterize the exfoliated structure and exfoliation degree are presented.

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40

Morard, Guillaume, Jean-Alexis Hernandez, Marco Guarguaglini, Riccardo Bolis, Alessandra Benuzzi-Mounaix, Tommaso Vinci, Guillaume Fiquet et al. "In situ X-ray diffraction of silicate liquids and glasses under dynamic and static compression to megabar pressures". Proceedings of the National Academy of Sciences 117, n. 22 (15 maggio 2020): 11981–86. http://dx.doi.org/10.1073/pnas.1920470117.

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Abstract (sommario):

Properties of liquid silicates under high-pressure and high-temperature conditions are critical for modeling the dynamics and solidification mechanisms of the magma ocean in the early Earth, as well as for constraining entrainment of melts in the mantle and in the present-day core–mantle boundary. Here we present in situ structural measurements by X-ray diffraction of selected amorphous silicates compressed statically in diamond anvil cells (up to 157 GPa at room temperature) or dynamically by laser-generated shock compression (up to 130 GPa and 6,000 K along the MgSiO3glass Hugoniot). The X-ray diffraction patterns of silicate glasses and liquids reveal similar characteristics over a wide pressure and temperature range. Beyond the increase in Si coordination observed at 20 GPa, we find no evidence for major structural changes occurring in the silicate melts studied up to pressures and temperatures exceeding Earth’s core mantle boundary conditions. This result is supported by molecular dynamics calculations. Our findings reinforce the widely used assumption that the silicate glasses studies are appropriate structural analogs for understanding the atomic arrangement of silicate liquids at these high pressures.

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41

Krüger, Hannes, Peter Tropper, Udo Haefeker, Reinhard Kaindl, Martina Tribus, Volker Kahlenberg, Christoph Wikete, Martin R. Fuchs e Vincent Olieric. "Innsbruckite, Mn33(Si2O5)14(OH)38 – a new mineral from the Tyrol, Austria". Mineralogical Magazine 78, n. 7 (dicembre 2014): 1613–27. http://dx.doi.org/10.1180/minmag.2014.078.7.06.

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Abstract (sommario):

AbstractA description of the new mineral innsbruckite, Mn33(Si2O5)14(OH)38, a hydrous manganese phyllosilicate found in Tyrol, Austria is given. The crystal structure was determined by singlecrystal synchrotron radiation diffraction experiments at the X06DA beamline at the Swiss Light Source (Paul Scherrer Institute, Villigen, Switzerland). The space group is Cm and lattice parameters are a = 17.2760(19), b = 35.957(5), c = 7.2560(8) Å , β = 91.359(7)º, V = 4506.1(10) Å3, Z = 2. Innsbruckite belongs to the group of modulated 1:1 layer silicates and is chemically and structurally quite closely related to bementite, Mn7(Si2O5)3(OH)8. The chemical analysis revealed a close to ideal composition with only minor amounts of Al, Fe and Mg. Using Liebau’s nomenclature for silicate classification the silicate anion can be described as an unbranched siebener single layer. Innsbruckite shows a complex topology of the silicate sheet, exhibiting 4-, 5-, 6- and 8-membered rings. The silicate sheet is fully characterized using vertex symbols, and its topology is compared to those in other complex sheet silicates. Furthermore, the structural investigation is complemented with Raman spectroscopic studies.

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42

Mennella, Vito, e Tushar Suhasaria. "H2 formation on Mg-rich amorphous silicates". Proceedings of the International Astronomical Union 15, S350 (aprile 2019): 109–13. http://dx.doi.org/10.1017/s1743921319008834.

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AbstractWe present the results of an experimental study on the interaction of D atoms with Mg-rich amorphous silicates. The effects of D irradiation have been analyzed by infrared spectroscopy. The results indicate that HD forms by abstraction of hydrogen atoms chemisorbed in the hydroxyl groups of silicate grains. The formation process occurs for grain and atom temperatures relevant to photodissociation regions.

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43

Vereshchagin, V. I., e T. S. Petrovskaya. "TRADITIONS AND PERSPECTIVES OF THE TECHNOLOGY OF SILICATES AND NANOMATERIALS DEPARTMENT". Steklo i Keramika, n. 13 (gennaio 2023): 47–50. http://dx.doi.org/10.14489/glc.2023.01.pp.047-050.

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Abstract (sommario):

The article provides a brief historical outline of the activities of the Technology of Silicates and Nanomaterials Department of the National Research Tomsk Polytechnic University which is the first technical university in the Asian part of Russia. Initially, the Laboratory of Chemical Technology of Mineral Substances, since 1929 the Silicate Technology Department, since 2007 the Technology of Silicates and Nanomaterials Department, nowdays it is one of the leading scientific and educational centers of the country for the study of silicate raw materials, the development of advanced technologies for ceramics, binders and glass materials, and the training of engineers and scientists specializing in the relevant fields. Research areas of the team embrases now the development of materials and technologies for nanostructured technical and building ceramics with enhanced functional properties, foam glass-ceramic materials, proppants for oil and gas production, biomedical ceramics, magnesian binders with increased strength and water resistance.

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Tang, Tao, Huo Gen Huang e De Li Luo. "Solid-State Reaction Synthesis and Mechanism of Lithium Silicates". Materials Science Forum 654-656 (giugno 2010): 2006–9. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2006.

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Abstract (sommario):

Lithium-based ceramics have been recognized as promising tritium breeding-materials for D-T fusion reactor blankets. Lithium silicates, Li4SiO4 and Li2SiO3, are recommended by many ITER research teams as the first selection for the solid tritium breeder. The solid-state reaction method is the most important way to synthesize lithium silicates. In present study, the processes of solid-sate reaction between amorphous silica and Li2CO3 powders was investigaed by TGA/DSC; the lithium silicate powders were synthesized at 700~900°C with different Li:Si molar ratio using solid-state reaction method. The optimized synthesis temperature and the solid-state reaction mechanism were derived on the base of experimental results.

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45

Esteban Benito, Heriberto, Ricardo García Alamilla, Juan Manuel Hernández Enríquez, Francisco Paraguay Delgado, Daniel Lardizabal Gutiérrez e Pedro García. "Porous Silicates Modified with Zirconium Oxide and Sulfate Ions for Alcohol Dehydration Reactions". Advances in Materials Science and Engineering 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/325463.

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Abstract (sommario):

Porous silicates were synthesized by a nonhydrothermal method, using sodium silicate as a source of silica and cetyltrimethylammonium bromide as a template agent. Catalysts were characterized using thermogravimetric analysis, N2physisorption, X-ray diffraction, FTIR spectroscopy, pyridine adsorption, potentiometric titration withn-butylamine, scanning electronic microscopy, and transmission electronic microscopy. The surface area of the materials synthesized was greater than 800 m2/g. The introduction of zirconium atoms within the porous silicates increased their acid strength from −42 to 115 mV, while the addition of sulfate ions raised this value to 470 mV. The catalytic activity for the dehydration of alcohols yields conversions of up to 70% for ethanol and 30% for methanol.

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Shchipalkina, Nadezhda V., Igor V. Pekov, Natalia N. Koshlyakova, Sergey N. Britvin, Natalia V. Zubkova, Dmitry A. Varlamov e Eugeny G. Sidorov. "Unusual silicate mineralization in fumarolic sublimates of the Tolbachik volcano, Kamchatka, Russia – Part 2: Tectosilicates". European Journal of Mineralogy 32, n. 1 (29 gennaio 2020): 121–36. http://dx.doi.org/10.5194/ejm-32-121-2020.

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Abstract. This second of two companion articles devoted to silicate mineralization in fumaroles of the Tolbachik volcano (Kamchatka, Russia) reports data on chemistry, crystal chemistry and occurrence of tectosilicates: sanidine, anorthoclase, ferrisanidine, albite, anorthite, barium feldspar, leucite, nepheline, kalsilite, sodalite and hauyne. Chemical and genetic features of fumarolic silicates are also summarized and discussed. These minerals are typically enriched with “ore” elements (As, Cu, Zn, Sn, Mo, W). Significant admixture of As5+ (up to 36 wt % As2O5 in sanidine) substituting Si is the most characteristic. Hauyne contains up to 4.2 wt % MoO3 and up to 1.7 wt % WO3. All studied silicates are hydrogen-free, including mica and amphiboles which are F-rich. Iron-bearing minerals contain only Fe3+ due to strongly oxidizing formation conditions. In Tolbachik fumaroles, silicates were formed in the temperature range 500–800 ∘C as a result of direct deposition from the gas phase (as volcanic sublimates) or gas–rock interactions. The zonation in distribution of major silicate minerals observed in a vertical section of the Arsenatnaya fumarole, from deep (the hottest) to upper parts is diopside + forsterite + enstatite + andradite → diopside → fluorophlogopite + diopside → sanidine + fluorophlogopite → sanidine. This is in agreement with volatilities of major species-defining metals in volcanic gases. From a crystal-chemical viewpoint, this series corresponds to the following sequence of crystallization of minerals with temperature decrease: nesosilicates → inosilicates → phyllosilicates → tectosilicates.

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Ghio, A. J., T. P. Kennedy, A. R. Whorton, A. L. Crumbliss, G. E. Hatch e J. R. Hoidal. "Role of surface complexed iron in oxidant generation and lung inflammation induced by silicates". American Journal of Physiology-Lung Cellular and Molecular Physiology 263, n. 5 (1 novembre 1992): L511—L518. http://dx.doi.org/10.1152/ajplung.1992.263.5.l511.

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Inhalation of silicates induces a variety of lung diseases in humans. The molecular mechanism(s) by which these dusts cause disease is not known. Because several naturally occurring mineral oxides have large amounts of transition metal ions on their surfaces, we tested the hypothesis that surface complexation of iron may be an important determinant of their ability to induce disease. Silica, crocidolite, kaolinite, and talc complexed considerable concentrations of Fe3+ onto their surfaces from both in vitro and in vivo sources. The potential biological importance of iron complexation was assessed by examining the relationship between surface [Fe3+] and the ability of silicates to mediate oxidative degradation of deoxyribose in vitro, induce a respiratory burst and elicit leukotriene B4 (LTB4) release by alveolar macrophages (AM) in vitro, and cause acute alveolitis after intratracheal insufflation. For these studies, three varieties of silicate dusts were used: iron-loaded, wetted (unmodified), and deferoxamine-treated to remove Fe3+. The ability of silicates to catalyze oxidant generation in an ascorbate/H2O2 system in vitro, to trigger respiratory burst activity and LTB4 release by AM, and to induce acute lung inflammation in the rat all increased with surface complexed Fe3+. The results of these studies suggest that surface complexation of iron may be an important determinant in the pathogenesis of disease after silicate exposure.

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Zulputra, Zulputra, e Nelvia Nelvia. "KETERSEDIAAN P, SERAPAN P DAN SI OLEH TANAMAN PADI GOGO (Oryza sativa. L) PADA LAHAN ULTISOL YANG DIAPLIKASIKAN SILIKAT DAN PUPUK FOSFAT". JURNAL AGROTEKNOLOGI 8, n. 2 (10 febbraio 2018): 9. http://dx.doi.org/10.24014/ja.v8i2.3351.

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The research was conducted from August 2014 to Januari 2015 in the Ultisol Land, Pematang Berangan Village, Rokan Hulu Regency, Riau Province. The study aims to determine the availability of P, P and Si uptake by upland rice plants granting silicate and phosphate fertilizer on Ultisol land. The form of this research is experimental factorial completely randomized design consist of two factors. The first factor is silicate consists of four levels (0, 50, 75, and 100 kg SiO2/ha), while the second factor is phosphate fertilizer consists of four levels (0, 36, 54, and 72 kg P2O5/ha), each combination was repeated three times. The results showed that administration of silicates and phosphates increase the availability of P, P and Si uptake of upland rice crop. Giving of 100 kg SiO2 and 36 kg P2O5 per hectare increase uptake of P and Si, each respectively increased by 208 % and 218 % compared without silicates and phosphates fertilizer.

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Ramamurthy, Sundar, Brian C. Hebert e C. Barry Carter. "Olivine-MgO interfaces produced by crystallization of glass fulms on single-crystal MgO substrates". Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 agosto 1995): 342–43. http://dx.doi.org/10.1017/s0424820100138087.

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Glassy silicates are present at grain boundaries in almost all liquid-phase sintered ceramic oxides. In many cases, the amorphous-crystalline interfaces in the sintered microstructure can be modified by inducing crystallization of the glassy phase. The intergranular phases in polycrystalline MgO are typically silicates with cations of calcium, magnesium and iron in the silicate network. A systematic approach to study the crystallization behavior of glass-MgO interfaces has been attempted in the present study. Following the work by Mallamaci in which crystallization of a silicate glass in contact with A12O3 was studied, devitrification of glass in contact with single-crystal MgO has been investigated. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterize the resulting microstructures.A pellet of Mg2SiO4 (forsterite) prepared by hot-pressing MgO and SiO2 powders was used as the target for depositing glass films onto single-crystal MgO substrates by pulsed-laser deposition (PLD). Glass films with the composition of olivine.

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Manakova, N. K., e O. V. Suvorova. "Obtaining of heat-insulating materials based on silica-containing waste with the addition of dolomite". Вестник гражданских инженеров 17, n. 6 (2020): 149–55. http://dx.doi.org/10.23968/1999-5571-2020-17-6-149-155.

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The paper presents the results of the study of feasibility of obtaining high-quality foamed thermal insulation materials based on a silicate matrix with addition of dolomite. It has been found out that the preliminary activation of a suspension based on a silica-containing component at a temperature of 90°C for 5-7 minutes allows accelerating the coagulation of silica fume and the synthesis of sodium silicates. Optimal foaming conditions for the charge frothing are 650-700°C for 25 minutes. There have been obtained foam silicates with a relatively uniform finely porous structure and stable physical and technical properties with density 0.38-0.48 g/cm³, strength up to 3 MPa, thermal conductivity 0.048-0.054 W/(m·K).

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